(1) Field of the Invention
The present invention relates to a rubber composition, and more particularly a rubber composition containing novel furnace carbon black and having a good reinforcing property and a remarkably improved resistance against heat build-up.
(2) Description of the Prior Art
It is commonly known that rubber articles, such as tires and the like, are generally formed of a plurality of rubber members, and that the rubber members are required to have different performances. In order to satisfy necessary requirements, it is necessary to select properly the kind and amount of carbon black to be contained in a rubber composition constituting the rubber members.
In the carbon black, the specific surface area and structure are important properties. For example, carbon black having a large specific surface area has an improved reinforcing property (wear resistance), but is poor in resistance against heat build-up. Carbon black having a large structure has a high modulus of elasticity, but is poor in fatigue resistance and cut resistance. That is, carbon black, which can satisfy both the reinforcing property and the resistance against heat build-up, or satisfy both the modulus of elasticity and the fatigue resistance and the cut resistance, has not yet been found.
Recently, resource saving and energy saving are socially demanded, and investigations for developing automobiles with low gasoline consumption are directed not only to the improvement of engines, but also to low fuel consumption tires which are low in power loss.
In order to satisfy the above described demands, rubber compositions having a low heat build-up have recently been demanded more and more, and various investigations for modifying polymers and the like have been recently predominantly carried out. However, there is a risk, in the modification a polymer, of deterioration of properties other than the heat build-up of a rubber composition.
The inventors have made various investigations with respect to carbon black which is contained, as an essential component, in a rubber composition used in tires and other rubber articles, and found out that when carbon black having a low heat build-up is used, substantially all kinds of polymers can be used, and rubber compositions having a low heat build-up can be easily produced depending upon the use purpose. The inventors have made further various investigations based on the above discovery, and found out that some of the properties of carbon black other than its specific surface area and structure have a high influence upon the heat build-up and reinforcing property of rubber, and accomplished the present invention.